Indoor Air Unit
PO Box 64975
St. Paul, MN 55164-0975
651-201-4601
www.health.state.mn.us
Recommended Best Practices for Mold
Investigation in Minnesota Schools
Environmental Health Division Indoor Air Unit
Updated May 2014
Table of Contents
EXECUTIVE SUMMARY ............................................................................................................1
INTRODUCTION ..........................................................................................................................2
PROCEDURE FOR SCHOOL DISTRICTS’ INITIAL INVESTIGATION OF MOLD .............3
STEP  CONTACTINDOORAIRQUALITYCOORDINATOR.......................................3
STEP  PROBLEM BACKGROUND EVALUATION......................................................3
STEP  INVESTIGATION ....................................................................................................4
STEP  MOLD CLEANING AND REMOVAL....................................................................5
STEP PROFESSIONALMOISTUREINVESTIGATION ................................................8
STEP PROFESSIONALMOLDINVESTIGATION..........................................................8
APPENDIX A: Rationale for Recommendations.........................................................................10
APPENDIX B: Background on Mold and Health Effects...........................................................12
APPENDIX C: Personal Protection and Contaminant Control...................................................14
APPENDIX D: Interpretation of Mold Testing Results..............................................................17
APPENDIX E: Expectations for Professional Mold Investigations............................................21
APPENDIX F: Mold Remediation References ...........................................................................25
APPENDIX G: Minnesota Contact Information .........................................................................26
APPENDIX H: Glossary of Terms..............................................................................................26
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Disclaimer
The views presented in this document are solely the responsibility of the Minnesota Department
of Health. The contents are intended to be used only as guidance. They are not a legal mandate
and should not be construed to imply any liability. The recommendations in this document are
also subject to change if more information becomes available.
Acknowledgments
The Minnesota Department of Health wishes to acknowledge and thank the following
individuals for their time, insightful comments and valuable feedback in the development of the
first version of this document (2001).
Mr. David Abrams; ARS Environmental Health, Inc.
Mr. Phil Allmon; Minnesota Department of Education
Mr. Bill Angell; University of Minnesota
Ms. Carol Bridley; Zumbrota-Mazeppa Public Schools
Mr. Wane Baker; Michael’s Engineering, Inc.
Mr. Michael Berry; Kenan Institute of Private Enterprise at University of North Carolina
Mr. Terry Brennan; Camroden Associates, Inc.
Mr. Clive Brown; U.S. Centers for Disease Control
Mr. Neil Carlson; University of Minnesota
Mr. Todd Christianson; Minnesota Department of Employee Relations
Mr. Paul Ellringer; Tamarack Environmental, Inc.
Ms. Connie Hayes; LaCrescent-Hokah Public Schools
Mr. Jim Kubisiak; Minnesota Department of Employee Relations
Mr. Mike McGuinness; RK Occupational & Environmental Analysis, Inc.
Mr Ken Meyer; Minneapolis Public Schools
Mr. MacGregor Pearce; Mold Sampling and Diagnostic Service, Indoor Air Quality
Investigations
Mr. Jed Waldman; California Department of Health Services
Mr. Bill Wooley; Independent School District #299
© MDH 2014. This document is copyrighted in the public domain. MDH requests that any
duplication of this document be done in its entirety. Citations should also reference the entire
document.
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EXECUTIVE SUMMARY
Indoor mold problems are complex issues, and Minnesota public schools have to respond to the
variety of concerns that are raised when such problems are suspected. The goal of this document
is to assist school district staff in their initial efforts to investigate the causes and severity of
such problems for the purpose of finding appropriate cost-effective solutions.
A key message of this document is that from a health perspective schools should rarely, if ever,
need to conduct mold testing in their initial investigation of a mold problem. Briefly, the main
reasons for this position are that:
•
Mold growth simply should not be tolerated in schools -- when such growth
is evident, the critical cause (excess moisture) should be corrected and the
mold removed as quickly as can be done in a safe and effective manner;
•
Mold testing rarely answers difficult questions about health risks and the need
for building evacuation;
•
Such testing often leads to unrealistic expectations that can’t be met;
•
There are other practical and cost-effective methods for identifying many of
the conditions which need intervention; and
•
The key to solving a school mold problem will always be to correct the source
of excess moisture and remove mold contamination – very often, these can be
achieved reasonably well without mold testing.
There can be situations where mold testing is valuable or otherwise warranted, for example to
“justify” remediation expenditures or protect parties from liability. In addition, properly
performed testing may be useful in finding hidden growth or non-visible contamination. If mold
testing is performed, it is critical that the investigation goals are clearly understood, achievable,
and focused on solving the problem. MDH recommends that school district staff inform
themselves adequately to be active participants in decisions about any mold testing done in their
facilities to ensure that results will be useful in correcting the problem.
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INTRODUCTION
The Minnesota Department of Health (MDH) developed this guidance at the request of the
Minnesota Department of Education (MDE). The goal of this document is to assist school staff
in responding to problems related to indoor mold. Its focus is on practical, cost-effective
methods to identify problems and assess the causes. The main objective of any mold
investigation should be to locate sites of indoor mold growth in order to determine how to best
control the underlying moisture problem and remove the contamination.
Mold contamination in the indoor environment is a complex and evolving issue that currently
involves a great deal of uncertainty. This guidance is only intended to represent “best practices”
advice of a general and conceptual nature. When extensive hidden mold growth is present or
when problematic contamination has spread beyond the initially identified areas, these
guidelines alone may not be sufficient. This document does not provide comprehensive
guidance on remediation of severe mold contamination. The document is not intended to be
applied to settings other than Minnesota schools.
There will be instances when mold testing is performed – hopefully for sound reasons. In
addition, “investigative” techniques not described in this document may be used to assist
remediation efforts. However, it is important for district staff to understand that it is better not to
test for mold, unless both sampling and interpretation of the data can be done in a way that
meets the investigation objectives with an acceptable degree of certainty.
The procedures on pages 3 through 9 are intended to help district staff perform or oversee an
investigation of a suspected mold problem. Steps 1- 3 are actions that can often be done by
district staff with limited resources. The principles in Step 4 and Appendix C are provided to
help district staff determine if in-house remediation is appropriate. If the district decides that the
problem warrants outside remediation help, these sections can help schools make sure that
contractors and consultants are meeting the district’s goals. Steps 5 and 6 describe expectations
for professional investigation of indoor mold and its causes.
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PROCEDURE FOR SCHOOL DISTRICTS’ INITIAL INVESTIGATION OF
MOLD
The Minnesota Department of Health (MDH) recommends that school district staff use the
following steps (pages 3 to 9) during their initial efforts when responding to a known or
suspected mold problem. Each step should be considered in the order presented.
Excess moisture is the core underlying cause of any indoor mold problem. It is critical to
address any catastrophic water problem as soon as possible, drying efforts should begin
immediately and materials should be substantially dried within 24 to 48 hours.
STEP  CONTACT INDOOR AIR QUALITY COORDINATOR
All Minnesota public school districts are required to have a person assigned the role of Indoor
Air Quality (IAQ) Coordinator. The IAQ Coordinator should be the first point of contact for all
complaints or suspicions of mold problems within the district. MDH is available to provide
technical advice to the school if requested by the administration.
STEP  PROBLEM BACKGROUND EVALUATION
It is critical in the early stages of a mold investigation that the school staff remains objective, resisting the temptation to attribute problems and complaints to the most obvious or most easily
found explanations.
Follow your district’s Indoor Air Quality Management Plan throughout the response. Under guidance of the Plan, ask plenty of questions to gather background information1 on the problem, including such details as:
 What is the nature of the reported problem? Is it visible mold, water
damage, odors, symptoms, or other?
 Who reported the problem?
 Where and when has the problem occurred? Include dates and weather
conditions.
 What has been observed by the person(s) reporting the problem?
 Who else has observed the problem?
 What symptoms, if any, are reported and by whom? Include timing, location,
frequency, severity, and duration.
Use the information gathered to form an initial assessment of the situation and begin
1
School district staff and any contractors/consultants hired by Minnesota public schools should be aware of and follow
any applicable legal requirements under the Data Practices Act (Minnesota Statutes, Chapter 13) for information they
collect. This statute may require that all information collected during an investigation be made available upon request.
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developing hypotheses. A concern reporting form, such as the one from MDH, could be used.2 Evaluate what is known, and decide what other information may still be needed to
understand and resolve the problem. Make certain that the “needs” identified are logical and
realistic. If mold growth is visible and its extent is confidently understood, go to STEP
. Visible mold also may indicate the presence of other moisture-related biological
pollutants such as bacteria, pests and dust mites.
STEP  INVESTIGATION
If the problem and its source is not obvious, or symptoms or other evidence of excess moisture
to suspect mold growth, school staff should investigate the suspected areas by performing a
careful walkthrough. The following activities are recommended:
 A visual check for mold growth. The appearance of mold may include many
textures or colors. Growth may appear as a solid patch or discrete colonies.
 A visual check for signs of excess moisture or water damage such as leaks,
warping, standing water, staining, condensation, efflorescence, corrosion of metal,
and dampness to the touch.
 The use of your sense of smell to locate sources of odors. “Mold odors” are
typically described as “earthy” or “musty”. Not all mold growth produces
noticeable odors and dormant or dead mold will not be odorous. However, when
such odors are detected they are a reasonable indicator of mold, bacteria and
dampness.
 Examine or survey suspected areas with a moisture meter to determine locations
of elevated moisture within materials. Pay attention to colder surfaces, slab
floors, hidden spaces, and areas of poor air circulation. Note that a measurement
of relative humidity in room air is not necessarily an indicator of the amount of
humidity or condensation available to mold growing on a cool surface.
School staff should be able to carry out the early phases of an investigation, but the skills of an
indoor air or moisture expert may also be needed in some cases.
An investigation should include all areas where moisture sources may be present such as crawl
spaces, utility areas, tunnels, and air plenums. If these areas fit the definition of a confined
space, please observe relevant safety requirements. Other areas with potential water intrusion or
moisture include roofs, windows, doors, skylights; moisture accumulation on cool condensing
surfaces; plumbing; steam pipes, and mechanical air handling and cooling systems.
Moldy environments do not always have visible growth on easy-to-see surfaces. Mold
commonly grows hidden within enclosed spaces or other areas that are difficult to view.
Consequently, visual inspection and odor assessment may also require careful destructive or intrusive efforts to inspect areas such as the following:
2
See the ‘Attachment 2. Example Concern Reporting Form’ at
www.health.state.mn.us/divs/eh/indoorair/schools/plan/index.html
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 Behind, under, and within cabinets, shelving units, storage lockers, and other
furnishings.
 Under carpet and pad, especially when covering, or installed over, an on-grade
or sub-grade slab.
 Above ceiling tiles.
 Behind wall coverings such as wallpaper and paneling.
 Within duct work, chases, risers, tunnels, plenums.
 Within wall cavities.
 Inside appliances and mechanical systems.
When using destructive techniques to investigate for mold, it is important to take precautions to
minimize disturbance of mold colonies and damage to building materials. Staff should make small
openings and attempt to examine interior spaces with the help of flashlights, mirrors, boroscopes
or other tools. Careful handling implies working slowly and gently to disturb contaminated
material as little as possible.
From a public health perspective, there is no practical reason to test visible mold growth found
in a school. Instead, resources should be used to promptly remove growth by cleaning or
disposal. Bulk, contact or tape lift samples may be appropriate in some circumstances where it is
“necessary” to verify that a suspected material is mold in order to justify expenditures or
corrective steps.
Appendix C contains recommendations and advice regarding the need for personal protective
equipment and contaminant control. MDH strongly advises that school staff consider these
issues before proceeding with investigation activities that may physically disturb mold growth or
other contaminants such as lead and asbestos. If applicable to investigation activities, safety
requirements for confined space entry should also be anticipated and must be followed.
STEP  MOLD CLEANING AND REMOVAL
The following is not meant to be a complete discussion of mold remediation. MDH’s companion
guidance document can be used: ‘Recommended Best Practices for Mold Remediation in
Schools’. Appendix F also lists several guidance documents which describe mold remediation in
more detail.
Prior to engaging in any mold cleaning or removal, school decision makers need to consider the
potential health threats and the possibility of worsening problems if clean-up of extensive
contamination is not properly planned or performed. School staff should use a graded approach
calling for greater protective measures with increasing: a) amount of contamination; b) chance
that contaminants will be released to the air due to physical disturbance of the growth; and c)
likelihood that occupants will come into contact with contaminated surfaces or air. The basis for
making such determinations invariably involves professional judgment and requires an
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understanding of the problem. Appendix C describes some of the most important considerations for protection of occupants and workers and for the control of contaminants.
The school has the final authority concerning how a mold problem is handled in its facilities.
That decision is largely a matter of judgment and depends on many situation-specific factors including budget considerations, potential liability, the perceived nature and extent of the
problem, and the skill, experience and level of care that can be expected of those doing the
work. MDH strongly recommends that experienced, trained and skilled staff perform the mold removal work when contamination is extensive or beyond the abilities of the school staff.
However, when small amounts of mold growth are found, school staff should be able to remove
contamination by carefully applying the following general procedures.
 Identify source(s) of excess moisture and begin to remove excess moisture as
soon as possible, or go to STEP  if professional assistance is needed.
 Correct source(s) of, and reasons for, excess moisture. This may be costly and
may require system changes and structural repairs.
 Trap or capture as much surface mold growth as possible from accessible
surfaces as soon as visible mold is found:
o Vacuum all visible mold growth using a HEPA vacuum; a shop vacuum
is not adequate.
o Carefully and systematically damp clean surfaces to remove and
capture surface growth. Work damp, not wet.
 Determine if the material(s) supporting surface mold growth can be cleaned
or should be removed and discarded:
o Porous3 materials (including “manufactured” or “processed” wood
products) – remove, enclose in plastic sheeting or bag, and discard all
porous materials, goods and furnishings which have or had visible
mold growth or strong mold odors.
o Non-porous materials (including solid wood items) – thoroughly clean all
visible growth and soiling from non-porous surfaces which have or had
visible mold by scrubbing with an all-purpose cleaner or detergent
solution (for final wiping steps, use clean water).
Expand cleaning to areas and materials in the vicinity of the visible mold growth.
This includes areas where it is likely that occupant traffic or activities may have
carried contaminants from the primary sites of growth. Use methods that can
capture and trap mold particles, such as HEPA vacuuming and damp cleaning (no
sweeping, dry dusting, brushing).

Determine if disinfection is needed or desirable. For example, when hard-surfaced
3
Hard surfaced porous materials such as finished wood products, cement, and concrete can often be left in place
provided they can be cleaned well, disinfected (optional) and thoroughly dried. If “manufactured” or “processed” wood
products and solid wood are structurally sound, are difficult to replace and are only lightly contaminated on the
surface, a thorough cleaning, disinfection, drying and optional sealing may be successful provided the material can be
kept dry in the future.
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porous materials are impractical to replace, such as concrete or cement walls or
floors, they should be disinfected with a dilute [5-10%] hypochlorite bleach solution4
or stronger after cleaning as described above. The solution should be applied by light
misting or wiping on to avoid runoff; treat the entire area that supported visible
growth. The surfaces should be kept damp with the solution for at least 30 minutes
and ideally up to two hours, rinse, then allow to air dry. Since bleach is actually a
poor cleaning agent and can be inactivated by organic matter, it is critical to
thoroughly clean off visible growth and soiling before disinfecting.
 Allow or facilitate complete drying of all materials wet from excess moisture,
cleaning activities, or disinfection solution. Dehumidifiers, fans, and ventilation with
dry warm air are among the methods that may be used to speed drying. Complete
drying to normal levels may take days or weeks.
 Perform final inspection for signs of continuing presence of excess moisture and/or
return of mold growth before rebuilding or refurnishing. If growth reappears, repeat
cleaning steps and disinfect again using a stronger bleach solution and allowing
longer contact time. Consider that regrowth may indicate that the material supporting
the growth should be removed and/or that excess moisture has not been controlled
adequately.
 Communicate with the public, school staff, and others as specified in the school’s
Indoor Air Quality Management Plan. Keep all stakeholders informed about findings
and progress throughout the investigation and cleanup process.
4
A suggested bleach solution for initial use is a 20:1 or a 10:1 dilution of standard household bleach with water. A
20:1 dilution (1 part bleach to 20 parts water) yields about a 5% bleach solution. A 10:1 dilution (1 part bleach to 10
parts water) will yield about a 10% bleach solution.
Bleach is a strong oxidizing agent that can corrode, etch or discolor some materials. If harm to surfaces is anticipated,
other disinfectants may be used as substitutes.
WARNING: Bleach should never be mixed with other chemicals unless the product label indicates it is safe.
Bleach should never be combined with any ammonia-containing product because chlorine gas will form. Always
provide proper ventilation when using chemical cleaners and disinfectants. Users must wear protective gloves when
using bleach solutions to avoid skin burns.
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STEP PROFESSIONALMOISTURE INVESTIGATION
Assessment and correction of the source(s) of excess moisture is absolutely critical to solving
and attempting to prevent the reoccurrence of an indoor mold problem. A building performance
or moisture expert may be needed when moisture problems cannot be identified or resolved by
district staff. District staff and the consultant should determine clear objectives for the moisture
investigation and ensure that the goals support those of the mold investigation effort. The
consultant should be asked to provide the following:
Expectations for Professional Moisture Investigation
 Conduct a thorough inspection of the facility/suspected problem area;
 Trace water/moisture pathways to source(s), if possible;
 Conduct moisture testing appropriately;
 Recommend specific actions to correct and prevent moisture problems; and
 Provide a written report or communication to the school district detailing
investigation procedure, findings and specific recommendations.
The school district should apply the findings and recommendations from any professional
moisture investigation to the clean-up response outlined in STEP .
STEP PROFESSIONALMOLDINVESTIGATION
From a health perspective, schools should rarely, if ever, need mold testing in their initial
investigation of a mold problem. See Appendix A for further explanation and the rationale for
this position. However, testing might be performed for reasons which are not health-based or
scientific; for example, to “justify” remediation expenditures or protect parties from future legal
liabilities. In addition, if problems consistent with indoor mold persist after the practical
measures described in steps  and  have been completed; appropriate and properly performed
testing may be valuable in locating additional hidden growth or non-visible contamination.
If mold testing is performed, it is critical that the investigation goals are clearly understood,
logical and achievable. Testing for mold should not be conducted unless an objective case can
be made for it as a necessary part of solving the problem. Experienced and competent
investigators should be able to justify any recommended mold sampling with a clear statement
of their hypothesis(es) and how the test results will be used in determining solutions to the
problem.
Schools that choose mold testing as part of their investigation should refer to the expectations
listed below and in Appendix E. Investigators should follow the guidance in Appendix E as they
plan and report on their activities in Minnesota schools, especially if the school foresees any
request to MDH for technical assistance on the situation.
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Expectations for Professional Mold Investigation
 Clearly designate and communicate objectives of all investigation activities
planned. The primary objective are to identify/determine:
o excess moisture accumulation and water intrusion;
o the presence of mold growth; and
o the extent of mold contamination.
 Gather background information regarding the site and problem history.
 Conduct visual assessment of the site and record observations.
 Establish, specify and follow sample collection and handling protocols appropriate
to meet investigation objectives.
 Establish, specify and follow quality control/quality assurance procedures.
 Provide results and detailed interpretation.
 Provide specific recommendations to:
o correct excess moisture sources and related problems (emphasizing the
critical importance of this);
o thoroughly clean and remove mold growth and related contamination; and
o address any other pre-determined objectives.
If mold testing is being considered as part of a school investigation, parties involved in
addressing the issue should weigh the pros and cons of testing before mold testing is conducted.
District staff should familiarize themselves with Appendices A and C. Competent
investigators are responsible for assisting the school district’s decision makers by: 1)
objectively educating them about what they really need from an investigation and how to best
achieve it, rather than simply responding to what they ask for; 2) describing the limitations of
any testing method, including the errors which can occur when too few samples are taken; 3)
describing the applicability of test results and the common uncertainties encountered in
interpreting results; and 4) managing the common false expectation that mold testing can
reliably predict safety concerns or rule out health risks
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APPENDIX A: Rationale for Recommendations
Schools should maintain a focus on solutions when investigating potential indoor mold
problems in their facilities. Efforts should rely mainly on the most practical and cost-effective
methods of finding mold growth and moisture problems that need correction. Contrary to
popular opinion, mold testing is often unnecessary and there is no practical health-based reason
to test visible mold growth once it is found.
While some mold testing may be useful when it is done properly, it should not be done unless
performed competently and for the purpose of testing specific hypotheses to aid in solving the
problem, such as, locating hidden mold growth or determining the extent of secondary
contamination. As a health-protective assumption, MDH suggests that any signs of mold
growth in schools be regarded as a potential health hazard which warrants corrective action,
regardless of the type of mold or amounts measured. Evidence of active mold growth inside a
school indicates that conditions exist which may foster the rapid growth and spread of mold,
some of which can be harmful to some people. Testing in a school should not delay prompt
corrective actions, nor should it divert resources from the practical solutions of moisture control
and thorough cleaning to remove mold contaminants.
The following provide the basis for cautioning against using limited school district resources on
indiscriminate, inadequately funded or poorly performed mold testing. In addition, these points
underscore the view that mold testing is inherently uncertain and cannot be relied upon to answer
questions about health and safety. Finally, the issues described below also illustrate some of the
limitations that investigators should be able to address in their sampling plan when they propose
mold testing as part of an investigation.
Point 1. The nature and quantity of contaminants present at, and released from, sites of mold
growth are typically dynamic and complex. When mold grows and multiplies indoors, the
contaminant mixture in the air or even that which is growing on, or deposited on, surfaces can be
very expensive to characterize because it may vary over time and space based on the following:
 Both the types of mold and their numbers in air or on surfaces are likely to vary with
an array of potentially changing micro-environmental factors such as temperature,
relative humidity, surface water activity level, type of substrate, nutrient availability,
presence of competing micro-organisms, and amount of light.
 The amount of mold products released to the air from a site of growth and how they
are distributed can change dramatically over short periods of time.
 The mixture of contaminants in the air can be influenced by factors such as ventilation
patterns, air speed and occupant activities, and will change over time and location as
the spores settle out at different rates.
 The deposition and accumulation of mold particles onto surfaces can depend on
releases from growth sites, airborne transport patterns, effectiveness of removal
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mechanisms and frequency of suspension caused partly by occupant activities such
as foot traffic or cleaning.
Point 2. Mold testing is incapable of completely characterizing and measuring the contaminant
mixture produced by most indoor mold problems. Because there are fairly reliable, practical and
cost-effective investigation techniques which don’t require mold testing, the following are
reasons to question the usefulness of mold testing in many school situations:
 Any test method is selective in which molds it can possibly detect out of the
broader universe of those molds that may be present -- consequently, testing results
cannot be relied upon to give a complete picture of all types of mold present.
 The quantities of mold detected (both the total numbers and relative frequencies) are
not precise counts; that is, the numerical results can vary by the sampling and
analytical method used, and should be regarded as fairly crude estimates at best.
 The results for any particular sample are only applicable to the specific time and
location of the sample – test results only represent a “snapshot” in time. They cannot
be assumed to estimate the contaminant load at a different location from where the
sample was taken and do not necessarily represent past or predict future conditions.
Point 3. It is fundamentally impossible to rule out mold-related health risks by any currently
available environmental testing methods. Even if it was practical to collect enough data to
identify and quantify all the mold present for a specific time and location, health risks and
occupant safety would not be fully understood or predicted due in part to the following:
 The identity of most mold species, and even strain or isolate, does not adequately
predict the amount or types of potentially harmful agents produced. A particular
mold that can produce harmful substances does not always do so -- and the types and
amounts it produces may change over time and from one location to another.
 Molds may produce agents which have not yet been identified or are not currently recognized as harmful.
 Mold testing results alone are not adequate to represent a person’s exposure to
mold particles or to the mold’s harmful products.
 Much remains unknown about how and why some individuals are affected by
mold when others are not, and what factors particular to the agent, the exposure,
and/or the person lead to health problems.
 Numerical criteria are not appropriate for determining if a health concern exists,
because there is no agreement on what minimum level of any specific mold,
much less a complex mixture of various organisms and their products, is safe or
is necessary to cause health effects.
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APPENDIX B: Background on Mold and Health Effects
Mold Growth
The term “mold” describes more than a million species of microscopic fungi that grow on wet or
damp organic matter, for example, paper, fabric, wood, cellulose-containing materials, insulation
or ceiling tiles. Several hundred of these organisms may be present in indoor environments. The
growth requirements for most indoor molds are relatively simple: oxygen (usually), suitable
temperature range, a supply of nutrients, and excess moisture. Moisture is the factor that is most
controllable and should be the focus of mold prevention and initial remedial efforts.
Mold grows on surfaces where excess moisture is available and on materials which can provide
organic nutrients. A visible growth of mold is called a colony. A material which is supporting
active growth and proliferation of colonies on its surfaces is called an amplifier. One of the ways
that molds reproduce and spread is by specialized microscopic cells called spores.
Many spores are very buoyant and readily dispersed by air movement. A single spore or other
viable mold particle can rapidly germinate, within days, to form a new colony – which in turn
can produce millions of additional spores.
Airborne and deposited mold particles are present throughout the environment – both outdoors
and indoors. Except when snow cover is present, molds from the outdoors are readily
transported into school facilities as air moves through doors and windows, as people carry
mold spores on their clothing, foot wear, and on other items that are brought into the
school building. Consequently, whenever mold testing is done, some mold is likely to be found;
however, the mere detection of mold in an indoor sample does not indicate that problematic
indoor mold growth is occurring. Finding indoor mold growth and favorable conditions for mold
growth are the real keys to determining if mold problems exist or are likely to occur.
Health Effects of Mold
Many molds can produce a variety of allergenic substances, odorous chemicals, and toxic
metabolites. The specific agents produced by mold that can affect human health are not always
predictable; they may vary in type, quantity, and strength from species to species and even from
one strain or isolate to another of the same mold species. For example, a colony that is
producing specific harmful agents at one time might not produce the same agents if the
conditions where it is growing change, or if it spreads to a new location with a different set of
micro-environmental conditions. The situation is further complicated by the fact that multiple
species of mold are often present when an indoor mold problem exists, and each species may be
influenced differently from the others as micro-environmental factors change.
In order for mold to affect health, it must contact or enter the body. People are mainly exposed
to mold by inhaling spores and by skin/eye contact. Actively growing mold may also release a
mixture of various volatile organic chemicals into the air that people breathe.
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When people are exposed to high levels of mold, especially when it proliferates indoors, a
spectrum of health effects may occur. Allergic symptoms are the most common problems, such
as mucous membrane irritation, rhinitis, and rashes. More severe effects, such as asthma attacks,
hypersensitivity pneumonitis, infections, or toxic reactions may also occur. However, since
susceptibility to the effects of molds varies in the population, health impacts from similar
exposures can vary greatly from person to person and may not be readily predictable for some
individuals and situations. Persons who are most likely to be susceptible include those with
respiratory problems such as allergies or asthma, a compromised immune system, the elderly
and the very young. MDH recommends that anybody who believes they have health
problems related to mold should seek professional medical attention.
Even when an indoor mold problem has been characterized as well as is possible, there will
always be uncertainty regarding if or how the health of occupants may be affected. In fact, for a
number of practical and logical reasons, the possibility that some portion of any group exposed
to molds will suffer adverse health effects can never be ruled out when mold is found growing in
occupied areas of a school. Given that there is considerable uncertainty about the health
consequences of exposure to contaminants from indoor mold problems, MDH recommends that
any mold growing inside a school be regarded as a sign of a potential (current or future) health
hazard that should be corrected properly as soon as possible.
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APPENDIX C: Personal Protection and Contaminant Control
PERSONAL PROTECTION:
When mold contaminated surfaces are physically disturbed, greatly elevated levels of airborne
mold particles often result. Such releases can occur during investigation, especially from
destructive efforts to get at hidden areas of growth, and clean-up activities. Workers performing
such mold related activities may breathe in or their skin may contact mold contaminants. In
general, the exposures to a mold worker or other school occupant will likely increase as the
amount of mold present increases and the more it is disrupted.
The Indoor Air Quality Coordinator in cooperation with the district’s Health and Safety staff, the regional Service Cooperative Health and Safety Management Assistance Professionals or
the Minnesota Department of Education should determine what type of personal protective
equipment is required5 for in-house staff and under what circumstances. If district staff are
unable to make such a determination, professional assistance should be sought. MDH
recommends that workers handling small amounts of moldy materials that are manageable by
routine custodial or building maintenance activities on an occasional short-term basis be
provided the following types of protective equipment, at a minimum:

Respiratory protection: A NIOSH-approved respirator capable of filtering
particles at least as small as 2 microns in diameter. An N-95 filtering face piece
respirator is recommended at a minimum. A half or full-face equipped with a
HEPA filtration cartridge (P-100) is strongly recommended when large areas of
contamination are expected to be disturbed.
 Eye protection; use goggles or a full-face respirator which excludes fine dusts.
 Skin protection; wear disposable or washable outer clothing, long sleeved
tops and long pants.
 Gloves; select those that are impervious to any chemicals used.
CONTAMINANT CONTROL:
It is critical, whenever investigation or cleanup activities expose and agitate moldy materials to
control the release and movement of mold particles and any other contaminants that are
liberated by the work. Such control is important to protect school occupants from exposure to
contaminants that may adversely impact their health and to prevent the spread of contaminants
into other areas of the building. Examples of pathways through which contaminants are spread
from their site of origin include movement via foot traffic leaving the contaminated area,
5
Currently there are no legal requirements for respiratory protection when handling indoor mold contamination in
Minnesota. However, when an employer requires the use of personal protective equipment, legal requirements
necessarily follow. For example, consult 29 CFR 1910.134 and 29 CFR 1926.109 for employer responsibilities when
employees are required to wear respiratory protection. For more information on mandated requirements, contact the
Minnesota Occupational Safety and Health Administration Workplace Safety Consultation unit at 651- 284-5060 or
[email protected]
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physical movement of improperly encased contaminated materials or by movement through the
air.
School staff should determine the need for contaminant control measures based upon the
likelihood that planned activities will disturb and/or disperse large quantities of mold particles
in areas where school occupants may be exposed. The following considerations may be useful
in evaluating the risks for a particular situation.
Determining the Need for Contaminant Control
 The amount, density of growth and size of area affected, of visible mold
growth and that which may be hidden;
 The amount of contaminants deposited on surfaces, such as carpet, from
past problems;
 The intensity and duration of physical forces that will be applied to the
contaminated materials and the likelihood that this will disturb the mold
and release contaminants into the air;
 The wetness of materials that will be disturbed -- wet materials may produce
less dusts than drier materials;
 The ability to enclose or cover contaminated materials before they are
disturbed;
 The proximity of the contamination to occupants – especially potentially
sensitive individuals;
 The existence of routes for airborne contaminants to reach occupied areas
(via planned pathways, such as ductwork, and unplanned pathways, such
as an air leakage caused by pressure differences;
 The length of time before remediation will begin and the expected
project duration;
 The proximity of contamination to items that would be very difficult or
costly to clean/remove if they become contaminated; and
 The skill, experience and level of care that may be expected of those doing
the work. MDH strongly recommends that experienced, trained or otherwise
skilled staff are used to perform the work when mold contamination is
extensive.
The following generalizations are intended to illustrate the two ends of the spectrum of options
for contaminant control. In the case of contamination that is limited to small and easily
accessible areas and which should be correctable by routine custodial or building maintenance
practices, only fairly limited contaminant control measures may be needed. In contrast, more
extensive measures are usually warranted when heavy or large scale contamination is expected
to become disturbed. While these examples may be used as guidance, specific needs must be
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determined on a case-by-case basis by the professional judgment of school district staff or their
consultants.
In the simpler cases, the following control methods may be used. These are best done before
performing activities that will physically disturb the areas of growth or as contamination is
gradually encountered and becomes accessible.
 Thoroughly vacuum all visible mold and materials surrounding the area of
growth using a HEPA vacuum;
 After vacuuming, damp clean surfaces in the area surrounding the growth;
Bag or cover areas of growth with plastic prior to removal of material; and
 Securely bag waste and dispose.
When contamination is extensive and will likely become airborne, the following methods may
also be warranted in addition to those above:
 Isolate the air handling system from the contaminated/work area;
 Construct containment6 around work area using plastic sheeting;
 Establish negative pressure inside the containment zone using HEPAfiltered ventilation equipment; and
 Test or monitor containment for leakage.
If district staff desire more detailed guidance on contaminant control, they should refer to one of
the documents listed in Appendix F, seek advice from an experienced professional remediation
service provider, or contact MDH.
DECONTAMINATION:
A protocol for decontaminating workers and equipment should be developed and in place before
beginning work that greatly disturbs mold contamination. The level of decontamination needed
for a given situation will depend on the nature and amount of contaminants, the type of activities
performed, and the use and arrangement of any containment around the work area. For example,
when removing personal protective equipment and tools or supplies from an area where elevated
airborne mold levels are expected, it is advisable that all such items be decontaminated or
bagged for disposal. Hard cleanable surfaces should be HEPA vacuumed and damp cleaned.
Clothing should be bagged for disposal or laundering.
6
Enclosing mold growth and contaminated materials within permanent structures is NOT recommended – on its own,
this containment will not control further mold proliferation or degradation of structural materials.
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APPENDIX D: Interpretation of Mold Testing Results
There are inherent problems with measuring the contaminant mixture that results from indoor
mold growth. Consequently, considerable uncertainty will exist that must be objectively handled
in the reporting and interpretation of any mold testing data. Any use of test results should
explicitly acknowledge sources of uncertainty and describe when subjectivity and opinion enter
into the interpretation. To maximize the utility of any7 testing performed to investigating a mold
problem in a school, MDH recommends that results be interpreted consistent with the following
principles, processes, and caveats.
QUALITATIVE ANALYSIS
The essence of qualitative analysis is to compare the types of mold species detected in an area
of interest, area of concern, against those detected in a comparable sample from an appropriate control8 area which is not expected to have problematic levels of mold. When the types of mold and relative proportion for each type differ significantly from those of the “control” sample, an area of indoor mold growth (fungal amplifier) is suspected as the source of the additional organisms.
 COMPARISON TO OUTDOOR CONTROL SAMPLES -- If mold species are found at
greater than one or two colony forming units in an indoor sample9 which are not present
in the outdoor control samples, this suggests an indoor source of mold growth. Note that
normally at least two outdoor control samples are recommended.
 COMPARISON TO INDOOR CONTROL SAMPLE -- If mold species are found in
greater than one or two colony forming units in a sample from an area of concern which
are not present in an indoor control/background sample, this suggests an indoor source of
mold growth may exist and have contributed contamination above the indoor background
levels.
QUANTITATIVE ANALYSIS
Quantitative analysis is based upon the number and concentration of molds found in the study
area compared to a comparable sample from appropriate control areas such as indoor control
and/or outdoor control locations. The total number of colony forming units and number per unit
for each species should be similar to, or less than, that found in the control samples. When
7
Bulk, contact or tease tape samples are sometimes collected for the sole purpose of confirming that a suspect material
is mold. These samples can be of value in an investigation and should only be interpreted as positive or negative for
the presence of mold growth in structures.
8
For the purposes of this document, the term “control” is roughly interchangeable with “reference”, “comparison” or
“background.” These terms are used to refer to samples taken from presumably uncontaminated areas. The fungal load
of a specific suspect media area may be partially assessed through a comparison to that in the uncontaminated areas.
However, for accuracy it is acknowledged that these are not true controls.
9
Raw values or actual counts of organisms should be considered in the interpretation of the results because the
concentration will depend on sampling duration. When raw numbers or actual counts for the sample indicate only one
or two spores of a species were detected, these can generally be disregarded unless their presence is confirmed in
several other samples. Repeat sampling may also need to be considered under these circumstances.
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sampling is done, at the very minimum 3 control samples should be collected—2-3 outdoor
control samples and 1 indoor control sample.
 COMPARISON TO OUTDOOR CONTROL SAMPLE -- The total number of colony
forming units should be less than that found in the outdoor control samples. Likewise, the
percentages of the total sample made up by each species should be similar to that found in
the outdoor sample. If there is a shift in the predominant species in the indoor samples,
there may be an indoor source of the molds that were found in greater numbers than in the
outdoor samples. It is important to consider whether the indoor area(s) are ventilated by
mechanical or natural means.
 COMPARISON TO INDOOR CONTROL SAMPLE -- The total number of colony
forming units should be similar to that found in an indoor control sample. Additionally,
the percentages of the total sample made up by each species should be similar to the
indoor control sample.
The degree to which the control samples are appropriate to characterize the “normal” or
background level and distribution of mold or the contribution from outdoors air to an indoor
location, greatly influences the ability to use the data. Appropriateness can be viewed in terms
of the timing, the location, and the number of samples used to characterize the fungal load of a
given site. For example, if an indoor area chosen for a control sample also has elevated levels
of mold, problems in either the control or suspect area may be masked in the comparison
process unless outdoor controls are also available. In addition, when selecting appropriate
outdoor control sample time and location for a building that is mechanically ventilated, “hold
up time” or the length of time for mold particles to travel from the outdoor intake to the indoor
sampling point, should also be considered. As described in Appendix E, mold investigation
reports should discuss the basis for selecting control sites and justify their use as an indicator of
“normal” or background levels.
The detection of only a few spores or colonies of a particular mold in a sample should only be
considered suggestive of an indoor source. In contrast, the confirmed presence of a particular
organism generally requires that: (a) it is found in several samples, (b) it is identified several
times in a single sample, or (c) there is visual evidence of/or source sampling indicating its
growth in the building. When the persistent presence of such organisms has been demonstrated,
schools must make decisions concerning safety on a case-by-case basis. All relevant
circumstances must be considered, including any information which may indicate that
occupants are, or will likely be, exposed to the mold.
Additional Notes:
Use of numerical guidelines is not recommended.
Various guidelines for interpreting mold sampling data have been developed, but scientific
consensus suggests that it is overly simplistic to rely solely on a comparison of test results to
numerical criteria. The applicability of any such guidelines should be specific to the media
sampled, sampling technique and all parameters, analytical method, growth/culture media,
geographic location, and building operation conditions such as natural ventilation versus filtered
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mechanical ventilation. At this time, MDH regards numerical guidelines for mold as arbitrary
and does not support their use as the sole basis for determining if an environment needs to be
corrected. Instead, visual evidence and building history should form the initial basis for
identifying most school mold problems.
Species-level identification is preferred.
Two names are used to describe a specific kind of mold; the first designates the genus and the
second denotes the species. As an analogy, genus is comparable to the make of a car and species
is the model. If the molds are identified only to genus (species not determined), comparisons of
control and non-control samples may fail to detect evidence of problems indicated by
differences between species of the same genus. In addition, some of the potential health hazards
of molds can differ depending on the species.
Identification of mold to the species level requires culturable sampling techniques which obtain
and allow germination and growth of viable mold propagules. Inherent limitations in such
methods include the increased time required for sample growth, the inability to detect nonviable mold particles, and the lack of a single sample growth media that allows all species to
compete well enough to be identified. Some labs may report species for samples analyzed
without culturing the molds, but these should always be viewed as a “presumptive
identification” at best.
Because speciation of some genera of molds can be quite costly, it may be preferable when
funds are severely limited, to ask if the laboratory will be able to “split” between two species
without naming them at no extra charge. In other words, in some cases the lab may be able
without much extra effort to distinguish two species as distinctly different. Depending on the
species present, this strategy may give enough detail to allow a more meaningful distinction of
mold types from one sample to another with less expense.
Identification of “red flag” organisms.
Certain species of mold are of particular interest when their presence is confirmed in an indoor
location because of their greater potential to cause health effects in some people. Indoor molds
commonly considered potentially hazardous include some of the following:
•
Species of Aspergillus (A. fumigatus, A. flavus, A. versicolor)
•
Species of Fusarium (F. moniliforme, F. solani, F. oxysporum)
•
Species of Penicillium (P. marneffei, P. chrysogenum, P. camembertii)
•
Species of Stachybotris (S. chartarum [also known as S. atra])
•
Alternaria alternata
The above is not a complete list of all molds that are significant to human health. Many other
molds can also cause health problems for some occupants under certain conditions. Furthermore,
there has been relatively little effort to date directed at identifying and testing the toxicity of the
myriad mold metabolites or constituent chemicals that are likely to exist. In other words, despite
current knowledge that certain organisms can cause problems for some individuals, the full
spectrum of health effects caused by most molds, even common species, is currently unknown.
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It is premature given the limited state of current knowledge to conclude that some types of
molds are necessarily of less concern from a health risk standpoint than those which have been
labeled by the popular media as “hazardous” or “toxic”. For this and other reasons, it is not
appropriate in the school setting to conduct testing solely for the purpose of attempting to find
out if so-called “dangerous” molds are present.
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APPENDIX E: Expectations for Professional Mold Investigations
The following is intended to be a suggestion of what school districts should expect and request
from consultants who provide mold investigation services, especially those which propose to
perform mold testing as part of their investigation. The expectations are presented in a format
resembling an investigation report. MDH recommends that school districts make these
expectations known early, so that activities are planned to ensure the district’s needs are met.
INTRODUCTION / BACKGROUND
The purpose of the introduction is to provide sufficient information about the problem to
demonstrate that the investigation efforts were warranted, logical, and the objectives were clear.
At a minimum, this section should include the following information:

Description of facility history, any past moisture problems and/or
occupant complaints;

Description of all information provided by the operators/occupants related to
the suspected problem or complaints;

Description of parties involved in the current or previous investigations;

Description of past issues already identified and how they were addressed;

Outline of current problem; and

Clear statement of the hypotheses and goals of the investigation.
SITE VISIT DESCRIPTION
Thorough visual assessment of the site is critical to a well-reasoned and logical investigation.
Information about the building’s history, especially concerning moisture problems and any
mold complaints, should be further evaluated during the inspection. Observations or
measurements should be recorded and described in sufficient detail to convey what was done
during the inspection and to demonstrate convincingly that the scope of inspection was
reasonably adequate to determine: (1) if visible mold colonies were present, (2) if mold odors
were detectable, and (3) if signs of current or past excess moisture were visible.
At a minimum, the site visit description should include the following information:
 Identification of persons interviewed or providing information;

Description of general building condition;

Identification of specific areas inspected and their normal or intended uses;

Description of building’s mechanical systems, especially those which serve
the areas being investigated;

Documentation of relevant current or past moisture problems including: high
relative humidity measurements especially at cold surfaces, condensation
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especially on colder surfaces, water content measurements, water stains,
decaying or warped wood, failing paint, peeling wall covering, roof leak,
plumbing leak, flooding, lack of conditioning of humid outdoor, leaking
windows;
 Description of any identified building system failures associated with moisture
intrusion, excess moisture build up, or high indoor humidity;
 Description of moisture migration pathways traced to sources as best as
possible;
 Description of visual observations of potential sources of mold contamination;
 Description of pathways for dissemination of particulate mold
contaminants or mold-produced volatile organic chemicals (odors); and
 Documentation of environmental conditions as well as the apparent
effectiveness of the HVAC system. Were all unit-ventilators operational?
Was a building designed to have air conditioning and was it operational?
SAMPLING/TESTING
NOTE: IN MOST CASES, MDH DOES NOT RECOMMEND MOLD SAMPLING AS PART
OF THE INITIAL EFFORTS TO INVESTIGATE POTENTIAL MOLD PROBLEMS IN
SCHOOLS. However, properly conducted testing and the information it can provide when used
appropriately may be useful and even necessary at some point in a school district’s response to
mold contamination issues.
When mold testing is performed, MDH believes that is critical that investigation goals are clearly
understood, logical and achievable. Unless there is a clear understanding of how test results will
be helpful and how they will be used to assist in correcting the problem, testing is likely to be
wasteful of scarce resources or worse yet, misleading. Experienced investigators and competent
consultants should be expected to justify any recommendation to collect mold samples and
should explain their reasoning and any underlying assumptions or anticipated limitations.
If environmental samples are collected to test for mold, the following minimum information
should be provided:
 Discussion of why sampling/testing is being performed.
 Description of how the data are to be interpreted and used to meet the objectives.
 Description of how the sampling protocol and choices achieved the objectives:
o Clear identification of sample locations and reason(s) chosen;
o Describe each sample collection method10 and reason(s) chosen;
o Describe sample media used and reason(s) chosen; and
10
If culturable bioaerosol sample results are to be interpreted by quantitative analysis, MDH suggests that species
level ID permits greater confidence in interpretation (see Appendix D).
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o Identify analytical procedures used and reason(s) chosen.

Description of QA/QC procedures used:
o Chain of custody for samples;
o Sample preservation methods;
o Date/time of sample analysis;
o Analytical methods; and
o Credentials of analyst/lab11.

Description of environmental conditions during and prior to sampling:
o Outdoor weather conditions;
o Temperature, relative humidity and dew point in the sampled space
o Occupation of space, type and level of activity;
o Windows open or closed; and
o HVAC system isolated or not.
FINDINGS AND INTERPRETATION
All data from sampling efforts should be reported in a clearly labeled format indicating sample
collection method, location, time and results. Raw data or actual counts should always be
reported. Extrapolated or values normalized to a per-sample unit basis can also be given, but
these should not be the only data reported. Results from quality control samples should also be
presented in the report along with the sampling data. Any laboratory notations relating to
samples or calculations performed on the data should also be provided with the sampling results.
A fairly complete interpretation of the data should be provided. For any environmental media
sampled for investigation purposes, MDH recommends that interpretation be consistent with the
principles described in Appendix D. It is also imperative that all limitations or qualifications
related to the data be clearly stated and all reasonable explanations or alternate interpretations be
objectively presented.
The findings should describe all excess moisture accumulation/water intrusion and mold
contamination identified or otherwise known. Where future excess moisture accumulation or
water intrusion is obvious or likely, this too should be pointed out. Visual observations of
moisture and/or mold contamination should be described along with any building system failures
found to be associated with excess moisture and water intrusion.
CONCLUSIONS AND RECOMMENDATIONS
This section should identify the source(s) of excess moisture which has allowed, is allowing, or
11
It is critical that samples be analyzed by a mycologist competent to provide the level of taxonomic identification
needed for the intended uses of the data. MDH suggests that laboratories used for analysis be, at a minimum,
accredited or certified by the American Industrial Hygiene Association’s EMLAP program. Note that being a
“participant” in the EMPAT program is not by itself an indication of competence.
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is likely to permit indoor mold growth. The section should also describe what the observations
and sample results objectively demonstrated about the presence of mold growth indoors, the
pathways for dissemination of mold particles or mold-produced volatile organic compounds in
occupied spaces, and the extent of areas that should be addressed to remove both viable and
non-viable mold contaminants.
Conclusions should logically follow from and refer back to the findings, especially the
observations reported. If evidence of indoor mold growth was identified, conclusions must
address the:
 source(s) of excess moisture that permitted mold growth and
 extent of mold contamination that warrants removal.
Recommendations should be consistent with and responsive to the conclusions. If indoor mold
growth was identified, the recommendations must include specific activities or procedures to:
 correct or eliminate source(s) of moisture that supported mold growth;
 remove all visible mold growth and any related contamination as prudent; and
 prevent further excess moisture accumulation or intrusion and/or future
mold growth.
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APPENDIX F: Mold Remediation References
There exist several mold remediation guidance documents which describe or recommend various
control measures based upon the extent or type of mold contamination. Many consultants and
service providers use the guidance described below. These materials can be used by schools at
their discretion if they feel more detailed advice on mold clean-up and removal is needed -- such
as when very heavy or widespread contamination is encountered. The following are examples of
such resources:
Recommended Best Practices for Mold Remediation in Minnesota Schools. Minnesota
Department of Health. June 2014.
Mold Remediation in Schools and Commercial Buildings. EPA 402-K-01-001, Reprinted
September 2008.
Guidelines on Assessment and Remediation of Fungi in Indoor Environments. New York
City Department of Health and Mental Hygiene, November 2008.
IICRC S500: Standard and Reference Guide for Professional Water Damager Restoration.
Institute of Inspection Cleaning and Restoration Certification, Third Edition, April 2006.
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APPENDIX G: Minnesota Contact Information
Minnesota Department of Health
Indoor Air Unit
PO Box 64975
St. Paul, MN 55164-0975
Phone: 651-201-4601 or 800-798-9050
Email: [email protected]
Minnesota Department of Education
Facilities and Technology/ School Finance
Phone: 651-582-8779
Email: [email protected]
Minnesota Service Cooperatives
Regions 1 & 2
Region 3
Region 4
Region 5
Regions 6 & 8
Region 7
Region 9
Region 10
Region 11
Northwest Service Cooperative
Northeast Service Cooperative
Lakes County Service Cooperative
National Joint Powers Alliance
Southwest/West Central Service Cooperative
Resource Training and Solutions
South Central Service Cooperative
Southeast Service Cooperative
Metro Educational Cooperative Services Unit
Thief River Falls
Mountain Iron
Fergus Falls
Staples
Marshall
St. Cloud
Mankato
Rochester
Minneapolis
Minnesota Department of Labor and Industry
Minnesota Occupational Safety and Health Administration
Workplace Safety Consultation Unit
Phone: 800-657-3776
Email: [email protected]
Note: MN OSHA does not regulate mold in the workplace, but does regulate personal
protective equipment use, training and other workplace practices associated with
hazards.
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APPENDIX H: Glossary of Terms
AMPLIFIER: An item (material, substrate, etc.) that supports the active growth and
proliferation (increase in numbers) of mold.
BIOAEROSOL: Airborne particles or matter of biological origin (derived from a live or
formerly living organism). For example, mold spores or fragments of a mold growth which are
suspended in the air.
CLEANING: The science and practice of controlling contaminants by locating, identifying,
containing, removing and disposing of unwanted substances from the environment.
COLONY: A uniform mass of cells all derived from a single cell and which is growing on a
solid surface. A colony is usually the smallest unit of mold that can be observed with the naked
eye.
CONTAINMENT: Barriers, seals, air-locks, negative air filtration systems and other methods
used to control the movement of airborne materials or agents and avoid secondary
contamination. For example, plastic sheeting used to enclose a work area to prevent disturbed
mold particles from drifting from the containment zone into adjacent or connected areas.
DISINFECTION: The elimination and destruction of microorganisms which may allow for
survival of some resistant organisms (e.g., bacterial endospores).
EFFLORESCENCE: Formation or presence of white crystalline material deposited on the face
of masonry.
ENCLOSURE: The practice of attaching a rigid and durable barrier to building components,
with all edges sealed for the purpose of permanently enclosing contaminants.
GENUS: A biological level of classification directly above the species level. In the practice of
naming mold, the genus is indicated first and is capitalized (e.g., Aspergillus is the genus of the
mold named, Aspergillus fumigatus). There often are many different species within a single
genus.
GENERA: the plural form of Genus.
HEPA: High efficiency particulate air. Capable of removal and capture of 99.97 % of dispersed
particles greater than or equal to 0.3 microns in size.
HYPERSENSITIVITY PNEUMONITIS: Abnormal sensitivity of the lungs to certain
environmental factors.
ISOLATE: An organism that has been grown from a particular sample.
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METABOLITE: A chemical produced by the metabolism of a living organism; produced by
enzymatic action.
MICRON: A unit of measure equal to one millionth (10-6) of a meter; also known as a
micrometer and written as “µm”.
MVOCs: Microbial Volatile Organic Compounds: a group of several organic chemicals that
can be produced by actively growing molds and bacteria and which are released as gases into
the air.
MYCOLOGIST: A person who studies or has “expert” knowledge of fungi.
MYCOTOXINS: A broad category of specialized fungal metabolites that can have harmful
effects on humans or animals. These are generally associated with the fungus itself, not with the
volatile products. Mycotoxins can be present in either living or dead spores or fragments and in
the materials on which the mold has grown. Each individual mycotoxin has its own spectrum of
potentially harmful effects.
PATHOGENIC: Capable of causing disease. The molds most often regarded as pathogenic are
those which are most frequently known to cause opportunistic fungal infections, primarily among
immune-compromised individuals (e.g., Aspergillus fumigatus).
POROUS: Strictly defined, porous refers to the ability of a material to allow fluids to pass
through (permeability to liquids or gases). For the purposes of this document, porous materials
are items which absorb moisture (liquid water or humidity). Examples include wood products,
paper products, fabric, carpet and pad, plasterboard, drywall, insulation, ceiling tiles.... In
contrast, non-porous materials include Formica, vinyl, plastic, glass, some tile, metal and many
other similar hard surfaced durable or sealed materials.
PROPAGULE: Particles that are capable of producing a colony (for example mold spores or
fragments of hyphae).
RELATIVE HUMIDITY (RH): A ratio demonstrating the actual amount of water present in
air: to the maximum amount of water that air (at the same temperature) is capable of holding;
this ratio is expressed a percentage. Warmer air has a greater capacity to hold water in the
vapor form than does cooler.
REMEDIATION: The spectrum of measures intended to correct a problem and restore the
environment to a useable state. For the purposes of this document, MDH regards mold
remediation as any combination of activities which: a) remove indoor mold growth and moldcontaminated materials, b) eliminate and prevent excess moisture that allows growth, and c)
rebuild or refurnish. For example, when mold growth that is limited to items that can be cleaned
or easily removed, remediation can consist of routine housekeeping and maintenance practices.
SPECIES: The next most specific level of biological classification below genus. In the
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practice of naming mold, the species follows the genus and its first letter is always written in
the lower case (e.g., fumigatus, in Aspergillus fumigatus).
SPORE: A specialized reproductive cell. Mold spores are individually microscopic and many
are very buoyant. As such, they readily stay suspended in the air and can be dispersed by air
movement.
STRAIN: A group of organisms within a species or variety, characterized by some particular
quality.
TAXONOMY: An orderly system for classifying and naming living organisms based upon how
closely groups or individuals are related. See also GENUS and SPECIES.
TOXIGENIC: Able to produce toxic substances. For example, some molds are toxigenic
(alternate term -- mycotoxigenic) and these may, under certain circumstances, produce
mycotoxins. Because toxigenic molds do not always produce toxins, the finding of toxigenic
molds in a sample does not necessarily demonstrate that toxins are being produced in the
sampled environment.
VIABLE: Able to maintain an independent existence. For example, a viable mold spore is
capable of reproducing a new colony after germination. Some mold spores can remain viable
for many years.
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